No one can or will guarantee that a gas well will never leak. You can find industry video narrated by one of those deep Walter Cronkite-like voices that tell you about the extraordinary precautions drillers take to protect the aquifer from migration of nasty stuff between layers.
You will find that extraordinary measures have been taken to shield drillers from liability and regulatory culpability. Exemptions have been carved out of the body of law intended to protect the environment. You will also find plenty of examples where the industry has obtained gag orders and non-disclosure settlements hoping to keep a lid on public knowledge of mistakes. There are even some egregious examples of perverse use of baseless law suits and even phony criminal charges to discourage public participation showcasing problems with drilling. As the cops say, “you can beat the wrap, but you can’t beat the ride.” (The “ride” is the whole process of being arrested and charged.) Even if one is obviously innocent of doing wrong, legal defense is costly and even if you win you end up out-of-pocket.
What’s behind all this? Independent peer-reviewed studies as well as industry studies show that at least six percent (6%) of fracking wells leak early in their life cycle. I strongly suspect that all wells will leak eventually – maybe not in 10 or 20 years, but in 100?
Let’s stick with what we know for the moment. Drilling puts a large hole through half a mile of ancient rock formations to reach the gas rich layer under Bucks County. It’s deeper elsewhere. At the surface level, where the aquifer is, at least three concentric steel casings line the bore hole. Cement under pressure is forced into the space between the outer casing and the rock to prevent gas and/or liquid from traveling vertically outside of the casing and moving between geologic layers. This cement is supposed to keep the nasty stuff out of the drinking water layers.
This is the fundamental weakness of the drilling system. Think about the cement you see in sidewalks, driveways, and foundations. It cracks. Cement is rigid and very strong in compression, but it doesn’t have good tensile strength. It doesn’t necessarily bond permanently to other materials. Voids, where there is no concrete seal, may be left when concrete is pumped into the annulus or gap around the well casing. It’s not like the footing for a house; you can’t look and see. Even with no disturbances cracks can open as the cement cures or long after it’s fully set. But there are disturbances. Seismic events happen regularly. The earth moves.
The drilling process itself involves huge rotating drill bits that pound and vibrate to chip the rock and open the hole. Boring generates heat that is carried away from the bit by the flow of drilling mud, a wet slurry pumped down the drill pipe bathing the cutting bit and carrying the chips and heat back up and out. So there is are temperature changes. Steel and cement don’t expand at the same rate. Drilling itself vibrates the upper casings components and the earth as the bore hole is extended downward. Time is money and sometimes drilling operators don’t wait long enough for the fresh cement to cure to full strength, fracturing the “green” cement as they resume drilling. Rust forms on the mild steel casings as dampness, chemicals, and natural acids do their work. The annulus space outside the casing isn’t clean. All of these conditions act to break the bonds between the casing and the cement, and loosen the cement from the bore hole walls.
Repeated fracking cycles subject the casing and the cement seal to strain. It’s hard to imagine that a steel pipe half a mile long doesn’t flex and move under these extreme pressure changes. The same hydraulic forces that are fracturing rock where the lateral pipe is perforated are also trying to fracture the seal around the well casing. Blowouts sometimes happen.
The casings come in sections and thread together. For more than fifty years the joints have been a problem when put under pressure. Engineers have optimized the shape an pitch of threads and used sealants. In spite of considerable experience and ingenuity, casing joints still fail.
Then there is outright reckless disregard for the consequences of leaks. Drillers have paid huge fines and settlements for blatant disregard for good practice and regulations. Critics say that inspection and enforcement is understaffed and too lax. Drillers sometimes even refuse to allow inspectors onto the drill site.
None of the precautions taken by even the most ethical drillers can ensure that a bore hole once created can be sealed permanently. Consequently every new well increases the probability of contamination of the aquifer forever. That probability starts with the first well at one-in-twenty odds (1:20) and the odds get worse over time. Each new well adds another leak possibility. It’s like playing repeated rounds of Russian roulette first with one gun, then two, and so on.
This is not a game we should want to play. The more I know about fracking, the more it looks like a bargain with the Devil. No matter how appealing the cheap energy is, in the long run we lose.[revised for clarity and to update links 7/10/15, 7/11/15.]